Weighbeam system



Filed Sept. 16, 1963 2 Sheets-Sheet 1 JJI r. P2 z 1 J OUTPUT TemperatureDifferential Pressure Transmitter PI'GSSUII'G Transmitter T m I I 17FLOW 2+ 17/ o, P T.

ORIFICE INVENTOR March 29, 1966 J. SORTEBERG WEIGHBEAM SYSTEM FiledSept. 16, 1963 2 Sheets-Sheet z Fol l Kessaru; $15M. ccNvezsro I gwmx 5Pmx Pmax max Emu- Fmt TEMFEKATUZE $(GNAL com 5am fanf= max Plane?ARALLELOGRAM or FOR6ES 5" K P CREATED BY KNEE Bki Kil' w United StatesPatent 3,243,112 WEIGHBEAM SYSTEM Johannes Sorteberg, Darien, Conn. (540Connecticut Ave., South Nor-walk, Conn.) Filed Sept. 16, 1963, Ser. No.309,061 3 Claims. (Cl. 235-200) The object of my present invention is todevise a novel control system or means for expressing mechanically theformula for a straight line, y=Kx+C (in a right angle coordinate systemwith x and y being the coordinates).

A further object of the invention is to use it as an auxiliary device ingas flow measurements when it is desired to compensate such measurementsfor absolute temperature and/ or pressure. A further object of theinvention is to devise a novel construtcion and arrangement of thecomponent parts to obtain'the results herein set forth.

For the purpose of illustrating the invention, I have shown in theaccompanying drawings a preferred embodiment of it which I have found inpractice to give satisfactory and reliable results; It is,howeyer,'to.beunderstood that the various instrumentalities of which theinvention consists can be variously arranged and organized and theinvention is not limited, except by the scope of the appended claims tothe exact arrangement and organization of these instrumentalities asherein set forth.

FIGURE 1 is a diagrammatic view of a weighbeam system embodying myinvention. 7

FIGURE 2 is an enlarged sectional view showing more clearly, theconstruction and arrangement of the kneebracket and its cooperatingparts.

FIGURE 3 is an exploded view of the parts seen in FIGURE 2.

FIGURE 4 is a diagram of transmitter signal (s) plotted against pressure(p) showing the relationship be tween the output signal from ahypothetical absolute pressure transmitter represented by line Z M andthe output signal from transmitter 17 represented by the line 0M.

- FIGURE 5 is a diagram of transmitter signal (s) plotted againsttemperature (t) showing the relationship between the output signal froma hypothetical absolute temperature transmitter represented by line Z Mand the output signalfrom transmitter 16, represented by line 0M. I

. FIGURE 6 is a'diagram showing the principle of the parallelogram offorces applied. to both pressure and temperature signal conversion.

Similar numerals of parts. g

Referring to the drawings:

Referring fiISLtoFIGURE 1. This figure shows .a mechanical embodiment ofthe invention as used in combination with a Force Bridge in a measuringcircuit. Only the principal elements of the Force Bridge are shown.

Refer to Patent No. 2,643,055 for complete details. F is the main frameof the Bridge. W and W are the weighbeams. R and R are the rollers whichprovide the movable fulcrums F and F A, B, C and D are the four forcesautomatically kept in balance in accordance with the Force Bridgeformula A C=B D, or

D C- XB I and II are similar load cells, each consisting of bellows 1 ina housing 2, mounted on a base 3, which in turn is mounted on a bracket4 supported on a frame F. Thrust rod 5 freely mounted in a tapered holein a kneebracket 6, and bearing against a ball 6 transmits the forcecreated by the load cell to said kneebracket supporting a shaft 7reference indicate corresponding 1 and bearing 8, the rim of which restsagainst a rotatable plane 9 which is journalled in bracket 4. A secondthrust rod 10 fixed in the other arm of kneebracket 6, transmits theforce originating in the load cell but modified by means of the planeand bearing in accordance with principle of parallelogram of forces (seeFIGURE 6). A spring 11 creates a force which is transmitted to rod 10through washer 12 and is adjustable by means of Washer 13, said washer13 being provided with a clearance from the kneebracket 6. This force isindependent of the force orginating in the load cell. Together theseforces create force A and/or B which are transmitted to the weighbeam.Load cells III and IV-consist only of parts similar to 1, 2, 3, and 5.Their thrust rods 5 act directly on weighbeam W A pipeline 14 has anorifice 15. A temperature transmitter 16 with range T to T transmitssignals 0 to scorresponding respectively to T and T to load cell I. Apressure transmitter 17 with a range P to P transmits signals 0 to Sp toload cell II. A differential pressure transmitter 18 with range d to dtransmits signals 0 to s to load cell IV. Load cell III transmits thecompensated output signal of the Force Bridge to its point of use. 1

With further reference to FIGURE 4 it should be noted that:

P =lower limit for pressure transmitter 17 P =upper limit for pressuretransmitter 17.,

K =tan QP= L u angle between OTI and (TE a =angle between WI andfil s=maximum signal from transmitter 17 a='constant=K P 1: any givenpressure within the range of transmitter 17 7 pl: p

With further reference to FIGURE S it should be noted that:

T =lower limit for temperature transmitter 16 'T =upper limit fortemperature transmitter 16 Briefly the system operates as follows:

Air is supplied to nozzles NL and NR which oppose weighbeam extensions,baffles 19 and 20. The back pressure from nozzle NL is transmittedthrough tube 21 to air motor AM which positions fulcrum rollers R and RThe back pressure from nozzle NR is transmitted through tube 22 to loadcell III and the output tube. Assume that both weighbeams are inbalance, i.e., A a=B b and D a=C b. If now, for instance, force Aincreases, bafiie 19 will move towards NL, increasing the back pressureand the air motor will move the fulcrum rollers to the left until W isagain in balance. This movement of the rollers will have the effect ofunbalancin-g W in such a way as to move bafiie 20 away from nozzle NRand dropping the back pressure, but this will decrease force C until Wis again in equilibrium or balance.

A typical example of the usefulness of the invention is in connectionwith gas flow measurements. The general formula for gas flow is:

wherein The above formula can also be written Q =c /E where P 1: d d

The Force Bridge is used to solve the formula P l: d d

with A representing T, B representing P, D representing d and Crepresenting d l. The force created by a load cell is equal to thesignal value multiplied by the effective area of the bellows, and Iwill, in order'to simplify matters, assume the effective area of eachload cell to be 1. Thus, I can substitute signal values for forces inthe formula, which can now be written In order to make temperaturecompensation for the gas volume in accordance with formula it isnecessary to produce a signal proportionate to the absolute temperaturevalues in the interval considered. This can be done in two ways: a

(1) Employ an absolute temperature transmitter pro? ducing an outputsignal at Z (absolute zero tempera-v ture) and a signal sTmax at Ttransmitting directly to a load cell similar to cells III or IV engagingthe weighbeams directly, or:

(2) Use a converter such as this invention covers in combination withtransmitter 16 to produce the absolute temperature signals in thetemperature span considered, T1 to T Similar consideration applies tothe pressure compensation.

By referring to FIGURE 4 it is evident that the signal valuesrepresenting the absolute pressure at any point P PP+ and similarly, byreference to FIGURE 5 the signal value representing the absolutetemperature at any point T isi In my construction the constants a and bare produced by the spring 11 and the variables are produced byrespective load cells in combination with their knee-brackets. (SeeFIGURE 6.)

In these equations:

max

I Should be n e t b urning h p an a tmnd the bearing axis, constants Kand K; can be made to have any value between 0 and 00. It should furtherbe noted h the above qu t ns $=KBV+ and =KTt+b oth represent straightlines, a general form of which is =K in a. right angle coor nate stemWith x and y as coordinates. K and C are constants,

Having thus described my invention, what I claim as new and wish tosecur y Letters Patent is:

1. A device for generating a variable function com.- prising, means e ci i a a ab e si na a d scavening it to a force, means for applying saidforce to, a paralr lelogram me h c ran eme t c m ri n n; n u

thrust member receiving said force, an output member,

a circular bearing articulated to said members and servin a a u r the ora a P ne u ac m u ted for adjustment tangentially to said circularbearing, said plane serving to modify the force input at the inputmember to produce an output at said output member proportionate to thetangent of the angle between the input member and a perpendicular tosaid plane surface and means for applying a further adjustable force tosaid output member.

2. A device according to claim 1 wherein the first force applied to saidoutput thrust member represents the product of the input force and thetangent of the afore: said angle and wherein said further force is addedt9 said product, 1 a

3. A device according to claim lwherein said input and output thrustmembers are in a perpendicular rela tionship'to each other.

References Cited by the Examiner UNITED STATES PATENTS 2,643,055

LEO SMILOW, Pr'imary Examiner. I

T. J. ANDERSON, Assistant Examiner.

1. A DEVICE FOR GENERATING A VARIABLE FUNCTION COMPRISING, MEANS FORRECEIVING A VARIABLE SIGNAL AND CONVERTING IT TO A FORCE, MEANS FORAPPLYING SAID FORCE TO A PARALLELOGRAM MECHANICAL ARRANGEMENT COMPRISINGAN INPUT THRUST MEMBER RECEIVING SAID FORCE, AN OUTPUT MEMBER, ACIRCULAR BEARING ARTICULATED TO SAID MEMBERS AND SERVING AS A FULCRUMTHEREFOR, AND A PLANE SURFACE MOUNTED FOR ADJUSTMENT TANGENTIALLY TOSAID CIRCULAR BEARING SAID PLANE SERVING TO MODIFY THE FORCE INPUT ATTHE INPUT MEMBER TO PRODUCE AN OUTPUT AT SAID OUTPUT MEMBERPROPORTIONATE TO THE TANGENT OF THE ANGLE BETWEEN THE INPUT MEMBER AND APERPENDICULAR TO SAID PLANE SURFACE AND MEANS FOR APPLYING A FURTHERADJUSTABLE FORCE TO SAID OUTPUT MEMBER.